This is a new project in which we are studying DNA damage and repair caused by Chemical and physical carcinogens in cultured human cells. For example, using the alkaline elution technique, we have detected DNA-protein crosslinks in cells exposed to chromate-salts. DNA-protein crosslinks induced by trans-Pt (II) diamminedichloride appear to be repaired by the excision pathway since they are more persistent in the excision deficient cells, and because, in the presence of DNA repair polymerase inhibitor, DNA single-strand breaks only accumulate in normal cells. Comparative studies of DNA damage and repair using human bronchial epithelial and fibroblasts have been initiated. Emphasis is given to agents implicated in pulmonary carcinogenesis.